// vim: set sts=2 ts=8 sw=2 tw=99 et:
//
// Copyright (C) 2013, David Anderson and AlliedModders LLC
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//  * Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//  * Neither the name of AlliedModders LLC nor the names of its contributors
//    may be used to endorse or promote products derived from this software
//    without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

#ifndef _include_amtl_thread_local_h_
#define _include_amtl_thread_local_h_

#include <amtl/am-utility.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#ifdef _WIN32
# include <windows.h>
#else
# include <pthread.h>
#endif

namespace ke {

// Stores a per-thread value. In single-threaded mode (KE_SINGLE_THREADED),
// this is a no-op container wrapper.
//
// T must be castable to uintptr_t.
//
// When assigning to a ThreadLocal<T>, the assigment will automatically attempt
// to allocate thread-local storage from the operating system. If it fails, it
// will abort the program. If this is undesirable, you may call allocate()
// up-front and handle the error case manually.
//
// The number of thread local slots available to processes is limited (on
// Linux, it is generally 1024). It is best to use ThreadLocal sparingly to
// play nicely with other libraries.
//
// ThreadLocal will free the underlying thread-local storage slot in its
// destructor, but it is not an AutoPtr. It does not delete pointers. Since
// one thread's value is only observable from that thread, make sure to free
// the contained resource (if necessary) before the thread exits.
template <typename T>
class ThreadLocal
{
  public:
    void operator =(const T& other) {
        set(other);
    }

    T operator *() const {
        return get();
    }
    T operator ->() const {
        return get();
    }
    bool operator !() const {
        return !get();
    }
    bool operator ==(const T& other) const {
        return get() == other;
    }
    bool operator !=(const T& other) const {
        return get() != other;
    }

  private:
    ThreadLocal(const ThreadLocal& other) = delete;
    ThreadLocal& operator =(const ThreadLocal& other) = delete;

#if !defined(KE_SINGLE_THREADED)
  private:
    volatile int allocated_;

  public:
    ThreadLocal() {
        allocated_ = 0;
    }

    T get() const {
        if (!allocated_)
            return T();
        return internalGet();
    }
    void set(const T& t) {
        if (!allocated_ && !allocate()) {
            fprintf(stderr, "could not allocate thread-local storage\n");
            abort();
        }
        internalSet(t);
    }

#    if defined(_MSC_VER)
    ~ThreadLocal() {
        if (allocated_)
            TlsFree(key_);
    }

  private:
    T internalGet() const {
        return (T)reinterpret_cast<uintptr_t>(TlsGetValue(key_));
    }
    void internalSet(const T& t) {
        TlsSetValue(key_, cast_to_pointer<T>::cast(t));
    }
    bool allocate() {
        if (InterlockedCompareExchange((volatile LONG*)&allocated_, 1, 0) == 1)
            return true;
        key_ = TlsAlloc();
        return key_ != TLS_OUT_OF_INDEXES;
    }

    DWORD key_;

#    else
  public:
    ~ThreadLocal() {
        if (allocated_)
            pthread_key_delete(key_);
    }

    bool allocate() {
        if (!__sync_bool_compare_and_swap(&allocated_, 0, 1))
            return true;
        return pthread_key_create(&key_, nullptr) == 0;
    }

  private:
    T internalGet() const {
        return (T) reinterpret_cast<uintptr_t>(pthread_getspecific(key_));
    }
    void internalSet(const T& t) {
        pthread_setspecific(key_, reinterpret_cast<void*>(t));
    }

    pthread_key_t key_;
#    endif // !_MSC_VER

#else // KE_SINGLE_THREADED
  public:
    ThreadLocal() {
        t_ = T();
    }

    bool allocate() {
        return true;
    }

    T get() const {
        return t_;
    }
    void set(const T& t) {
        t_ = t;
    }

  private:
    T t_;
#endif
};

} // namespace ke

#endif // _include_amtl_thread_local_h_
